When a button is attached to a cloth, generally, the button is positioned over a horizontally-arranged cloth, a button-fixing member is supported by a lower die under the cloth, and a shaft of the button-fixing member pierce the cloth. Next, after the shaft has passed through an attachment hole of the button, an upper die coupled to a pressing machine is moved down towards the lower die, thereby the shaft being swaged through press-deformation by a bottom of the upper die. Japanese Examined Patent Laid-Open No. 61-43443 and Japanese Examined Utility Model Laid-Open No. 4-2979 disclose examples of conventional upper dies.
In the conventional upper dies, however, when the shaft of the button-fixing member is press-deformed for button-attachment, the shaft is deformed to radially outwardly expand in an entire circumferential direction. Therefore, if the cloth is thick, the outward radial expansion of the shaft fails, and there may be cases where enough button attachment power and button strength are not secured. On the other hand, if the cloth is thin, there may be a case where the shaft extends radially outwardly more than required to cause a surplus portion, resulting in that formability may be degraded.